Changes made via about:config are profile specific, i.e only apply to the profile that is selected when you open about:config and are stored in prefs.js in the profile folder. There is a way to use an autoconfig.cfg or policies.json file in the Firefox installation folder to deploy settings for all users and all profiles. *https://support.mozilla.org/en-US/kb/customizing-firefox-using-policiesjson *https://support.mozilla.org/en-US/kb/customizing-firefox-using-autoconfig *https://github.com/mozilla/policy-templates/blob/master/README.md